PROJECT ABSTRACT Houston experienced 50 inches of rain and record-breaking, catastrophic flooding from Hurricane Harvey. Importantly, this flooding caused uncontrolled releases into the environment from over a dozen Superfund sites and several chemical/petroleum facilities. In response to this disaster, we worked with affected communities to administer health questionnaires, deploy wristbands to detect chemical exposures, and collect biosamples for microbiome analysis for the first 30 days exposure window after flooding. Under this RFA mechanism, we now propose to build on this strong foundation of field experience, early exposure data, and community engagement with longitudinal time-sensitive sampling of nasal, oral and gut biospecimens from 300 individuals at 6- and 12-months post-Hurricane Harvey. These biospecimens and microbiome data will be used as part of time- sensitive disaster research response (DR2) activities, and stored as a unique resource for future microbiome- environment interaction studies. They will also be integrated with chemical exposure data obtained from wristband monitoring devices, and health outcome data from questionnaires administered to study participants. The human microbiome is both a target for, and a modifier of, response to environmental exposures. Consequently, microbiome research has begun to make significant contributions to our understanding of how microbiome-environment interactions impact risk for disease. Our Overarching Hypothesis is that during major disasters, such as the Hurricane Harvey flooding, environmental exposures are reflected in the microbiome of exposed individuals. If correct, this would predict that microbiome-environment interactions will be associated with adverse health outcomes, either causally or as correlative biomarkers, and can serve as a target or indicator for actionable, post-disaster activities. In Specific Aim 1, we will identify microbiome-environment interactions associated with adverse health outcomes. We will focus our initial analysis on the nasal microbiome, where we will test the hypothesis that data from the nasal mycobiome can inform both short- and long-term assessment of respiratory tract health. In Specific Aim 2, we will test the hypothesis that microbiome data better inform flood-related health outcomes than current environmental monitoring. In this Aim, we will ask whether microbiome analyses from biospecimens collected over the 12 month post-Harvey period reflects mold exposures from the home and effectiveness of remediation, and informs health outcome assessment by providing data not captured by wristbands or other environmental monitoring. In the future, these studies are expected to provide Preliminary Data for research aimed at 1) better understanding the role of the microbiome on post-disaster health outcomes, 2) identifying microbiome-based biomarkers of exposure(s) and/or health effects, and 3) improving decision-making by stakeholders and DR2 activities in response to future flood-related disasters.